This invention relates to pharmaceutically useful compounds, in particular compounds which are useful in the inhibition of cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDEs), such as type 5 cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDE5). The compounds therefore have utility in a variety of therapeutic areas, including male erectile dysfunction (MED).
EP-A-0636626 relates to a class of pyrazolo[3,4-d]-pyrimidone compounds and their use as inhibitors of cGMP specific PDE. A series of 6-phenylpyrazolo[3,4-d]pyrimidinones, their synthesis and their cyclic GMP phosphodiesterase inhibitory activity are described in J. Med. Chem., 1996, 39, 1635-1644. International patent application WO 96/16657 discloses the use of certain pyrazolo[3,4-d]pyrimidinone compounds (amongst others) in the treatment of MED.
EP-A-0526004 describes certain pyrazolo[4,3-d]pyrimidinone compounds as antianginal agents. International patent application WO 94/28902 discloses the use of certain pyrazolo[3,4-d]pyrimidinone compounds (amongst others) in the treatment of MED.
According to the present invention, there is provided a compound of general formula I: 
or a pharmaceutically or veterinarily acceptable salt and/or solvate thereof,
wherein
X represents O or NR5 
R1 represents H, lower alkyl, Het, alkylHet, aryl or alkylaryl (which latter five groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15)
R2 represents H, halo, cyano, nitro, OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13, SO2NR14R15, lower alkyl, Het, alkylHet, aryl or alkylaryl (which latter five groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15)
R3 represents H, lower alkyl, alkylHet or alkylaryl (which latter three groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15)
R4 represents H, halo, cyano, nitro, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13, NR16Y(O)R17, N[Y(O)R17]2, SOR18, SO2R19, C(O)AZ, lower alkyl, lower alkenyl, lower alkynyl, Het, alkylHet, aryl, alkylaryl (which latter seven groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15)
Y represents C or S(O)
A represents lower alkylene
Z represents OR6, halo, Het or aryl (which latter two groups are both optionally substituted with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15)
R10 and R11 independently represent H or lower alkyl (which latter group is optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10aR11a, NR10R11, SO2NR14R15 and NR20S(O)2R21 or Het or aryl optionally substituted with one or more of said latter thirteen groups) or one of R10 and R11 may be lower alkoxy, amino or Het, which latter two groups are both optionally substituted with lower alkyl
R10a and R11a independently represent R10 and R11 as defined above, except that they do not represent groups that include lower alkyl, Het or aryl, when these three groups are substituted and/or terminated (as appropriate) by one or more substituents that include one or more C(O)NR10aR11a and/or NR12R13 groups
R12 and R13 independently represent H or lower alkyl (which latter group is optionally substituted and/or terminated with one or more substituents selected from OR6, C(O)OR9, C(O)NR22R23 and NR24R25), one of R12 or R13 may be C(O)-lower alkyl or C(O)Het (in which Het is optionally substituted with lower alkyl), or R12 and R13 together represent C3-7 alkylene (which alkylene group is optionally unsaturated, optionally substituted by one or more lower alkyl groups and/or optionally interrupted by O or NR26)
R14 and R15 independently represent H or lower alkyl or R14 and R15, together with the nitrogen atom to which they are bound, form a heterocyclic ring
R16 and R17 independently represent H or lower alkyl (which latter group is optionally substituted and/or terminated with one or more substituents selected from OR6, C(O)OR9, C(O)NR22R23 and NR24R25) or one of R16 and R17 may be Het or aryl, which latter two groups are both optionally substituted with lower alkyl
R5, R6, R7, R8, R9, R18, R19, R20, R22, R23, R24 and R25 independently represent H or lower alkyl
R18 and R19 independently represent lower alkyl
R21 represents lower alkyl or aryl
R26 represents H, lower alkyl, aryl, C(O)R27 or S(O)2R28 
R27 represents H, lower alkyl or aryl
R28 represents lower alkyl or aryl
Het represents an optionally substituted four- to twelve-membered heterocyclic group, which group contains one or more heteroatoms selected from nitrogen, oxygen, sulpfur and mixtures thereof
which compounds are referred to together hereinafter as xe2x80x9cthe compounds of the inventionxe2x80x9d.
The term xe2x80x9carylxe2x80x9d, when used herein, includes six- to ten-membered carbocyclic aromatic groups, such as phenyl and naphthyl, which groups are optionally substituted with one or more substituents selected from aryl (which group may not be substituted by any further aryl groups), lower alkyl, Het, halo, cyano, nitro, OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10aR11a, NR12aR13a (wherein R12a and R13a independently represent R12 and R13 as hereinbefore defined, except that: (i) they do not represent C(O)Het in which Het is substituted by one or more substituents that include one or more C(O)NR10aR11a and/or NR12aR13a groups; or (ii) they do not together represent C3-7 alkylene interrupted by NR26) and SO2NR14R15.
The term xe2x80x9cHetxe2x80x9d, when used herein, includes four- to twelve-membered, preferably four- to ten-membered, ring systems, which rings contain one or more heteroatoms selected from nitrogen, oxygen, sulfor and mixtures thereof, and which rings may contain one or more double bonds or be non-aromatic, partly aromatic or wholly aromatic in character. The ring systems may be monocyclic, bicyclic or fused. Each xe2x80x9cHetxe2x80x9d group identified herein is optionally substituted by one or more substituents selected from halo, cyano, nitro, oxo, lower alkyl (which alkyl group may itself be optionally substituted or terminated as defined below), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10aR11a, NR12aR13a and SO2NR14R15. The term thus includes groups such as optionally substituted azetidinyl, pyrrolidinyl, imidazolyl, indolyl, furanyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, thiadiazolyl, triazolyl, tetrazolyl, oxatriazolyl, thiatriazolyl, pyridazinyl, morpholinyl, pyrimidinyl, pyrazinyl, pyridinyl, quinolinyl, isoquinolinyl, piperidinyl, pyrazolyl imidazopyridinyl and piperazinyl. Substitution at Het may be at a carbon atom of the Het ring or, where appropriate, at one or more of the heteroatoms.
xe2x80x9cHetxe2x80x9d groups may also be in the form of an N-oxide.
The heterocyclic ring that R14 and R15 (together with the nitrogen atom to which they are bound) may represent may be any heterocyclic ring that contains at least one nitrogen atom, and which ring forms a stable structure when attached to the remainder of the molecule via the essential nitrogen atom (which, for the avoidance of doubt, is the atom to which R14 and R15 are attached). In this respect, heterocyclic rings that R14 and R15 (together with the nitrogen atom to which they are bound) may represent include four- to twelve-membered, preferably four- to ten-membered, ring systems, which rings contain at least one nitrogen atom and optionally contain one or more further heteroatoms selected from nitrogen, oxygen and/or sulfur, and which rings may contain one or more double bonds or be non-aromatic, partly aromatic or wholly aromatic in character. The term thus includes groups such as azetidinyl, pyrrolidinyl, imidazolyl, indolyl, isoazoyl, oxazoyl, triazolyl, tetrazolyl, morpholinyl, piperidinyl, pyrazolyl and piperazinyl.
The term xe2x80x9clower alkylxe2x80x9d (which includes the alkyl part of alkylHet and alkylaryl groups), when used herein, means C1-6 alkyl and includes methyl, ethyl, propyl, butyl, pentyl and hexyl groups. Unless otherwise specified, alkyl groups may, when there is a sufficient number of carbon atoms, be linear or branched, be saturated or unsaturated, be cyclic, acyclic or part cyclic/acyclic, and/or be substituted by one or more halo atoms. Preferred lower alkyl groups for use herein are C1-3 alkyl groups. Alkyl groups which R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27 and R28 may represent, and with which R1, R2, R3, R4, R10, R11, R12, R13, R16, R17, aryl, alkylaryl, alkylHet and Het may be substituted, may, when there is a sufficient number of carbon atoms, be linear or branched, be saturated or unsaturated, be cyclic, acyclic or part cyclic/acyclic, be interrupted by one or more of oxygen, sulfur and optionally alkylated or optionally acylated nitrogen and/or be substituted by one or more halo atom. The terms xe2x80x9clower alkenylxe2x80x9d and xe2x80x9clower alkynylxe2x80x9d, when used herein, include C2-6 groups having one or more double or triple carbon-carbon bonds, respectively. Otherwise, the terms xe2x80x9clower alkenylxe2x80x9d and xe2x80x9clower alkynylxe2x80x9d are defined in the same way as the term xe2x80x9clower alkylxe2x80x9d. Similarly, the term xe2x80x9clower alkylenexe2x80x9d, when used herein, includes C2-6 groups which can be bonded at two places on the group and is otherwise defined in the same way as xe2x80x9clower alkylxe2x80x9d. The term xe2x80x9cacylxe2x80x9d includes C(O)-lower alkyl.
The terms xe2x80x9calkylHetxe2x80x9d and xe2x80x9calkylarylxe2x80x9d include C1-6 alkylHet and C1-6 alkylaryl.
The alkyl groups (e.g. the C1-6 alkyl groups) of alkylHet and alkylaryl may, when there is a sufficient number of carbon atoms, be linear or branched, be saturated or unsaturated, and/or be interrupted by oxygen. When used in this context, the terms xe2x80x9cHetxe2x80x9d and xe2x80x9carylxe2x80x9d are as defined hereinbefore. Substituted alkylHet and alkylaryl may have substituents on the ring and/or on the alkyl chain.
Halo groups with which the above-mentioned groups may be substituted or terminated include fluoro, chloro, bromo and iodo.
Compounds of general formula (I) can be represented by formulae IA and IB: 
wherein R1, R2, R3, R4 and X are as defined hereinbefore.
The pharmaceutically or veterinarily acceptable salts of the compounds of the invention which contain a basic centre are, for example, non-toxic acid addition salts formed with inorganic acids such as hydrochloric, hydrobromic, hydroiodic, sulphuric and phosphoric acid, with carboxylic acids or with organo-sulphonic acids. Examples include the HCl, HBr, HI, sulphate or bisulphate, nitrate, phosphate or hydrogen phosphate, acetate, benzoate, succinate, saccarate, fumarate, maleate, lactate, citrate, tartrate, gluconate, camsylate, methanesulphonate, ethanesulphonate, benzenesulphonate, p-toluenesulphonate and pamoate salts. Compounds of the invention can also provide pharmaceutically or veterinarily acceptable metal salts, in particular non-toxic alkali and alkaline earth metal salts, with bases. Examples include the sodium, potassium, aluminium, calcium, magnesium, zinc and diethanolamine salts. For a review on suitable pharmaceutical salts see Berge et al, J. to Pharm, Sci., 66, 1-19, 1977.
The pharmaceutically acceptable solvates of the compounds of the invention include the hydrates thereof.
Also included within the scope of the compound and various salts of the invention are polymorphs thereof.
A compound of the formula (I) contains one or more asymmetric carbon atoms and therefore exists in two or more stereoisomeric forms. Where a compound of the formula (I) contains an alkenyl or alkenylene group, cis (E) and trans (Z) isomerism may also occur. The present invention includes the individual stereoisomers of the compounds of the formula (I) and, where appropriate, the individual tautomeric forms thereof, together with mixtures thereof. Separation of diastereoisomers or cis and trans isomers may be achieved by conventional techniques, e.g. by fractional crystallisation, chromatography or H.P.L.C. of a stereoisomeric mixture of a compound of the formula (I) or a suitable salt or derivative thereof. An individual enantiomer of a compound of the formula (I) may also be prepared from a corresponding optically pure intermediate or by resolution, such as by H.P.L.C. of the corresponding racemate using a suitable chiral support or by fractional crystallisation of the diastereolsomeric salts formed by reaction of the corresponding racemate with a suitable optically active acid or base, as appropriate.
All stereoisomers are included within the scope of the invention.
A preferred group of compounds according to a further aspect of the invention, are compounds of formulae I, IA and IB as hereinbefore defined, wherein:
R1 represents H, lower alkyl, Het, alkylHet, or alkylaryl (which latter four groups are all optionally substituted and/or terminated with one or more substituents selected from cyano, lower alkyl, OR6, C(O)OR9 or NR12R13);
R2 represents H, halo, lower alkyl, Het or aryl (which latter three groups are all optionally substituted and/or terminated with one or more substituents as defined hereinbefore, and preferably with NR12R13 or SO2NR14R15);
R3 represents C1-C4 alkyl or C3-C4 cycloalkyl which are optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15);
R4 represents halo, cyano, nitro, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13, N[Y(O)R17]2, NR16Y(O)R17, SOR18, SO2R19, C(O)AZ, lower alkyl, lower alkynyl, Het or aryl, which latter three groups are all optionally substituted and/or terminated with one or more substituents as defined hereinbefore;
and wherein Y, A, Z, R10, R11, R12, R13, R14, R15, R16, R17, R5, R6, R7, R8, R9, R18, R19 and Het are as herein before defined.
Further preferred compounds herein are those in which R1 represents optionally substituted lower alkyl, more preferably lower alkyl, lower alkoxy-terminated lower alkyl, NR12R13-terminated lower alkyl, or N-morpholino-terminated lower alkyl. Alternatively, R1 may represent a 4-piperidinyl or a 3-azetidinyl group, optionally substituted at the nitrogen atom of the piperidinyl group with lower alkyl or C(O)OR9.
In such further preferred compounds of the invention, R2 represents C(O)NR10R11, NR12R13, lower alkyl optionally interrupted by one or more of O, S or N, optionally substituted at N by lower alkyl or acyl, or optionally substituted aryl or Het. More preferably, when R2 is interrupted lower alkyl, the interrupting atoms are one or more of O and lower alkylated-N and when R2 is aryl, it is optionally substituted phenyl or pyridyl.
Particularly preferred compounds of the invention are those in which R2 represents C(O)NR10R11, NR12R13, C1-4 alkyl optionally interrupted by O or N, optionally substituted at N by lower alkyl, optionally substituted phenyl, or optionally substituted pyridin-2-yl, pyridin-3-yl, pyrimidin-5-yl, pyrazin-2-yl, pyrazol-4-yl, oxadiazol-2-yl, furan-2-yl, furan-3-yl, tetrahydrofuran-2-yl and imidazo[1,2-a]pyridin-6-yl.
In the further and particularly preferred compounds of the invention, R3 may represent lower alkyl or cycloalkyl. Also, X is preferably O.
Such further and particularly preferred compounds of the invention have R4 representing halo, lower alkyl, lower alkynyl, optionally substituted Het, optionally substituted aryl, C(O)R8, C(O)AZ, C(O)OR9, C(O)NR10R11, NR12R13 or NR16Y(O)R17. More preferred values for R4 are C(O)R8 (e.g. acetyl), halo (e.g. iodo), SO2R19 (wherein R19 represents lower alkyl) and C(O)NR10R11 (e.g. where R10 and R11 independently represent H and lower alkyl and/or one of R10 and R11 is lower alkoxy) or NHB, wherein B represents H, SO2CH3 or C(O)Het.
Further preferred compounds of the invention include those in which R4 represents iodo, lower alkyl, lower alkynyl (which latter two groups are substituted and/or terminated by C(O)OR9 (wherein R9 represents H or C1-6 alkyl)), N(H)Y(O)R17, N[Y(O)R17]2, optionally substituted Het or NR12R13 (wherein R12 and R13 together represent C3-5 alkylene interrupted by O or Nxe2x80x94S(O)2-(optionally substituted aryl)).
Compounds of the invention that are more preferred still are include those in which R4 represents N(H)Y(O)R17 (wherein R17 represents C1-4 alkyl optionally substituted and/or terminated by C(O)OH or C(O)O-lower alkyl).
Preferred compounds of the invention include the compounds of Examples 1 to 87 described hereinafter (excluding the preparative examples). More preferred compounds include the compounds of Examples 1, 20, 22, 24, 32, 34, 44a, 44b, 44c, 63, 64, 65, 66, 67, and 85 and the compounds of Examples 5, 16, 17, 21, 26, 29, 47, 48, 49, 50, 50a, 51, 51a, 59, 68, 70, 71, 73, 74, 75, 77, 79, 80, 84, 86, 87, 89, 91, 92, 113, 114, 116, 118-128, 130-136, 138, 140, 143.
Highly preferred compounds herein include the following:
5-(2-Butoxy-5-iodo-3-pyridinyl)-3-ethyl-2-(2-methoxyethyl)-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(2-Butoxy-5-iodo-3-pyridinyl)-3-ethyl-1-(2-methoxyethyl)-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(5-Iodo-2-isobutoxy-3-pyridinyl)-2-methyl-3-propyl-2,6-dihydro-7H-pyrazolo[4,3-a]pyrimidin-7-one;
5-(2-Butoxy-5-iodo-3-pyridinyl)-2-[2-(4-morpholinyl)ethyl]-3-ethyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
tert-Butyl 4-[5-(2-butoxy-5-iodo-3-pyridinyl)-3-ethyl-7-oxo-6,7-dihydro -2H-pyrazolo[4,3-d]pyrimidin-2-yl]-1-piperidinecarboxylate;
tert-Butyl 3-[5-(2-butoxy-5-iodo-3-pyridinyl)-3-ethyl-7-oxo-6,7-dihydro-2H-pyrazolo[4,3-d]pyrimidin-2-yl]-1-azetidinecarboxylate;
5-(2-Propoxy-5-iodo-3-pyridinyl)-3-ethyl-7-oxo-6,7-dihydro-2H-pyrazolo-[4,3-d]pyrimidin-5-yl]nicotinate;
tert-Butyl [3-ethyl-5-(5-iodo-2-propoxy-3-pyridinyl)-7-oxo-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-1-yl]acetate;
tert-Butyl [3-ethyl-5-(5-iodo-2-propoxy-3-pyridinyl)-7-oxo-6,7-dihydro-2H-pyrazolo[4,3-d]pyrimidin-2-yl]acetate;
[3-Ethyl-5-(5-iodo-2-propoxy-3-pyridinyl)-7-oxo-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-1-yl]acetic acid;
[3-Ethyl-5-(5-iodo-2-propoxy-3-pyridinyl)-7-oxo-6,7-dihydro-2H-pyrazolo[4,3-d]pyrimidin-2-yl]acetic acid;
5-(2-Propoxy-5-iodo-3-pyridinyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
2-[2-(Dimethylamino)ethyl]-5-(2-ethoxy-5-iodo-3-pyridinyl)-3-ethyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
6-Butoxy-5-[3-ethyl-2-(2-methoxyethyl)-7-oxo-6,7-dihydro-2H-pyrazolo[4,3-d]pyrimidin-5-yl]-N-methoxy-N-methylnicotinamide;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-3-ethyl-2-(2-methoxyethyl)-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-[5-Acetyl-2-(2-methoxy-1-methylethoxy)-3-pyridinyl]-3-ethyl-2-(2-methoxyethyl)-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-3-ethyl-1-(2-methoxyethyl)-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
6-Isobutoxy-N,N-dimethyl-5-(2-methyl-7-oxo-3-propyl-6,7-dihydro-2H-pyrazolo[4,3-a]pyrimidin-5-yl)nicotinamide;
5-(5-Glycoloyl-2-isobutoxy-3-pyridinyl)-2-methyl-3-propyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-2-[2-(dimethoxyethyl)-ethyl]-3-ethyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-2-[2-(4-morpholinyl)-ethyl]-3-ethyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-2-[2-(4-piperidinyl)ethyl]-3-ethyl-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
tert-Butyl 4-[2-(5-(5-acetyl-2-butoxy-3-pyridinyl)-3-ethyl-7-oxo-6,7-dihydro-2H-pyrazolo[4,3-d]pyrimidin-2-yl)ethyl]-1-piperidinecarboxylate;
5-(5-Acetyl-2-butoxy-3-pyridinyl)-3-ethyl-2-(1-methyl-4-piperidinyl)-2,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
[5-(5-Acetyl-2-propoxy-3-pyridinyl)-3-ethyl-7-oxo-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-1-yl]acetic acid;
5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxynicotinonitrile;
1-Methyl-5-[2-propoxy-5-(1H-tetrazol-5-yl)-3-pyridinyl]-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
5-[5-(3-Hydroxy-5-isoxazolyl)-2-propoxy-3-pyridinyl]-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-a]pyrimidin-7-one;
5-(5-Amino-2-propoxy-3-pyridinyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;
{[5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxy-3-pyridinyl]amino}acetic acid;
N-[5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxy-3-pyridinylmethanesulfonamide;
N-[5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxy-3-pyridinyl]-3-oxo-xcex2-alanine;
({[5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxy-3-pyridinyl]amino}sulfonyl)acetic acid;
N-[5-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-6-propoxy-3-pyridinyl]alanine;
5-{2-[2-(Dimethylamino)ethyl]-3-ethyl-7-oxo-6,7-dihydro-2H-pyrazolo-[4,3-d]pyrimidin-5-yl}-6-ethoxynicotinic acid; and
5-{2-[2-(Dimethylamino)ethyl]-3-ethyl-7-oxo-6,7-dihydro-2H-pyrazolo-[4,3-d]pyrimidin-5-yl}-6-ethoxy-N-methoxy-N-methylnicotinamide.
An especially preferred group of compounds according to the present invention have the general formula (I) wherein:
X represents O or NR5;
R1 represents lower alkyl or alkylHet, which are optionally substituted and/or terminated with one or more substituents selected from lower alkyl, or NR12R13;
R2 represents lower alkyl, Het or aryl which are optionally substituted and/or terminated with one or more substituents as defined hereinbefore;
R3 represents C1-C4 alkyl or C3-C4 cycloalkyl which are optionally substituted and/or terminated with one or more OR6 substitutents;
R4 represents halo, cyano, C(O)R8, C(O)NR10R11, NR12R13, NR16Y(O)R17, SO2R19 or aryl, wherein said aryl group is optionally substituted and/or terminated with one or more substituents as defined herienbefore;
and wherein Y, A, Z, R10, R11, R12, R13, R16, R17, R5, R6, R8, R19 and Het are as herein before defined.
The compounds of the invention may exhibit tautomerism. All tautomeric forms of the compounds of formulae I, IA and IB, and mixtures thereof, are included within the scope of the invention.
The compounds of the invention may contain one or more chiral centres and therefore can exist as stereoisomers, i.e. as enantiomers or diastereomers, as well as mixtures thereof. The individual stereoisomers of the compounds of formulae IA and IB, as well as any mixtures thereof, are included within the scope of the invention. Diasterebisomers may be separated using conventional techniques e.g. by fractional crystallisation or chromatography. The various stereoisomers may be isolated by separation of a racemic or other mixture of the compounds using conventional techniques e.g. fractional crystallisation or HPLC. The desired optical isomers may be prepared by reaction of the appropriate optically active starting materials under conditions which will not cause racemisation or epimerisation. Alternatively, the desired optical isomers may be prepared by resolution, either by HPLC of the racemate using a suitable chiral support or, where appropriate, by fractional crystallisation of the diastereoisomeric salts formed by reaction of the racemate with a suitable optically active acid or base. All stereoisomers are included within the scope of the invention.
Also included within the scope of the invention are radiolabelled derivatives of compounds of formulae I, IA and IB which are suitable for biological studies.
The present invention additionally provides compounds of the general formulae (IA) and (IB) or a pharmaceutically or veterinarily acceptable salts and/or solvates thereof, wherein
X represents O or NR5 
R1 represents H, lower alkyl, Het, alkylHet, aryl or alkylaryl, which latter five groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14 R15 
R2 represents H, halo, cyano, nitro, OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13, SO2NR14R15, lower alkyl, Het, alkylHet, aryl or alkylaryl, which latter five groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR13R14 and SO2NR14R15 
R3 represents H, lower alkyl, alkylHet or alkylaryl, which latter three groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15 
R4 represents H, halo, cyano, nitro, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13, NR16Y(O)R17, SOR18, SO2R19R20, C(O)AZ, lower alkyl, lower alkenyl, lower alkynyl, Het, alkylHet, aryl, alkylaryl, which latter seven groups are all optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15 
Y represents C or S(O), wherein one of R16 and R17 is not present when Y is S(O)
A represents lower alkylene
Z represents OR6, halo, Het or aryl, which latter two groups are both optionally substituted with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR12R13 and SO2NR14R15 
R5, R6, R7, R8, R9, R18, R19 and R20 independently represent H or lower alkyl
R10 and R11 independently represent H or lower alkyl, which latter group is optionally substituted and/or terminated with one or more substituents selected from halo, cyano, nitro, lower alkyl, halo(loweralkyl), OR6, OC(O)R7, C(O)R8, C(O)OR9, C(O)NR10R11, NR10R11 and SO2NR13R15 or Het or aryl optionally substituted with one or more of said latter eleven groups or one of R10 and R11 may be lower alkoxy, amino or Het, which latter two groups are both optionally substituted with lower alkyl
R12 and R13 independently represent H or lower alkyl or one of R12 or R13 may be C(O)-lower alkyl or C(O)Het in which Het is optionally substituted with lower alkyl
R14 and R15 independently represent H or lower alkyl or R14 and R15, together with the nitrogen atom to which they are bound, form a heterocyclic ring
R16 and R17 independently represent H or lower alkyl or one of R16 and R17 may be Het or aryl, which latter two groups are both optionally substituted with lower alkyl
Het represents an optionally substituted four to twelve membered heterocyclic group, which may be aromatic or non-aromatic, which may contain one or more double bonds, which may be mono- or bi-cyclic and which contains one or more heteroatoms selected from N, S and O.
According to a further aspect of the invention there is provided processes for the preparation of compounds of the invention, as illustrated below.
The following processes are illustrative of the general synthetic procedures which may be adopted in order to obtain the compounds of the invention:
1. Compounds of formulae I, IA and IB may be prepared by cyclisation of corresponding compounds of formulae II, IIA and IIB, respectively: 
wherein R1, R2, R3, R4 and X are as defined previously for compounds of formulae I, IA and IB.
This cyclisation may be accomplished under basic, neutral or acidic conditions using known methods for pyrimidone ring formation. Preferably, the cyclisation is performed under basic conditions using an alkali metal salt of an alcohol or amine, such as sodium ethoxide, potassium tert-butoxide, cesium carbonate or potassium bis(trimethylsilyl)amide, in the presence of a suitable alcoholic solvent, such as ethanol, for example at reflux temperature (or, if performed in a sealed vessel, at greater than reflux temperature). The skilled person will appreciate that, when X represents O and an alcohol is selected as solvent, an appropriate alcohol of formula R3OH, or a sterically hindered alcohol, e.g. 3-methyl pentan-3-ol, may be used if it is intended to mitigate alkoxide exchange at the 2-position of the pyridin-3-yl.
Compounds of formulae II, IIA and IIB may be prepared by reaction of corresponding compounds of formulae III, IIIA and IIIB, respectively: 
wherein R1 and R2 are as defined previously for compounds of formulae II, IIA and IIB, with a compound of formula IV or a carboxylic acid derivative thereof: 
wherein R3, R4 and X are as defined previously for compounds of formula II, IIA and IIB.
This coupling reaction may be achieved by conventional amide bond forming techniques which are well known to those skilled in the art. For example, an acyl halide (e.g. chloride) derivative of a compound of formula IV may be reacted with a compound of formula II, IIIA or IIIB in the presence of an excess of a tertiary amine, such as triethylamine or pyridine, optionally in the presence of a suitable catalyst, such as 4-dimethylaminopyridine, in a suitable solvent such as dichloromethane or THF, at a temperature of about 0xc2x0 C. to room temperature.
A variety of other amino acid coupling methodologies may be used to couple the compounds of formulae II, IIIA or IIIB with the compound of formula IV. For example, the acid of formula IV or a suitable salt thereof (e.g. sodium salt) may be activated with an appropriate activating reagent, e.g. a carbodiimide, such as 1,3-dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride optionally in the presence of 1-hydroxybenzotriazole hydrate and/or a catalyst such as 4-dimethylaminopyridine; a halotrisaminophosphonium salt such as bromo-tris(pyrrolidinyl)phosphonium hexafluorophosphate; a suitable pyridinium salt such as 2-chloro-1-methyl pyridinium chloride; or another suitable coupling agent such as O-(7-azabenzotriazol-1-yl)-N,N,Nxe2x80x2,Nxe2x80x2-tetramethyluronium hexafluorophosphate (HATU). Either type of coupling reaction may be conducted in a suitable solvent such as dichloromethane, tetrahydrofuran or N,N-dimethylformamide, optionally in the presence of a tertiary amine such as N-methylmorpholine or N-ethyldiisopropylamine (for example when either the compound of formula III, IIIA or IIIB, or the activating agent is presented in the form of an acid addition salt), at from about 0xc2x0 C. to about room temperature. Preferably, from about 1 to 2 molecular equivalents of the activating reagent and from 1 to 3 molecular equivalents of any tertiary amine present may be employed.
Alternatively, the carboxylic acid function of IV may be activated using an excess of a reagent such as N,N-carbonyldiimidazole in an appropriate solvent, e.g. ethyl acetate, dichloromethane or butan-2-one, at from about room temperature to about 80xc2x0 C., followed by reaction of the intermediate imidazolide with either a compound of the formula II, IIIA or IIIB at from about 20xc2x0 C. to about 90xc2x0 C.
In a further variation, a compound of formula I, IA or IB, as defined previously, may be formed in a one-pot procedure by coupling a compound of formula III, IIIA or IIIB with the acyl chloride derivative of formula IV and by cyclising the resultant intermediate compound of formula II, IIA or IIB, using the methods as described previously. The one-pot procedure may further involve an in-situ coupling and cyclisation reaction to form a compound of formula I, IA or IB. Preferably, pyridine may serve as an acid scavenger and as the solvent for the in-situ coupling and cyclisation reaction.
According to preferred processes of the present invention, a compound of formula I, IA or IB, as defined previously, may be formed in a one-pot procedure as defined hereinbefore by coupling a compound of formula III, IIIA or IIIB with an acid derivative of formula IV and by cyclising the resultant intermediate compound of formula II, IIA or IIB, using the methods as described previously wherein the acid derivative of formula IV is formed from an ester of general formula (XXX) which itself is prepared either from a compound of general formula (XXXI) which is obtained from a compound of general formula (XXXII): 
or wherein IV is formed directly from a compound of general formula (XXXII) wherein RP is C1 to C6 alkyl, preferably methyl or ethyl and wherein RQ is a halogen, selected from Cl, Br and I, and is preferably I. These preferred processes according to the present invention are exemplified herein in Preparations 37, 56, 57, 58, 59, 61 and Example 129 herein. It is to be understood that the direct formation of IV from (XXXII) is the most preferred route.
In the above preferred processes preferred compounds of formulae (IV), (XXX), (XXXI) and (XXXII) are used wherein R3 is lower alkyl, preferably C2 to C4, X is O, RQ is a halogen, preferably Br or I, RP is a protecting group for an acid and is preferably a lower alkyl group such as methyl or ethyl or t-butyl, and R4 is acyl, preferably acetyl.
Compounds of formulae II, IIA and IIB may alternatively be prepared by alkylation of corresponding compounds of formulae XXIII, XXIIIA or XXIIIB, respectively, as defined hereinafter, for example under conditions such as those described hereinafter in respect of the preparation of compounds of formulae I, IA and IB (see process 5).
2. Compounds of formulae I, IA and IB, in which R2 represents C(O)NR10R11, and R10 and R11 are as defined previously for compounds of formulae I, IA and IB, may be prepared by reaction of corresponding compounds of formulae I, IA and IB, in which R2 represents C(O)OH (or a carboxylic acid derivative thereof) with a compound of formula HNR10R11, in which R10 and R11 are as previously defined for compounds of formulae I, IA and IB.
This reaction may be accomplished using analogous amide bond forming techniques to those previously described for compounds of formulae II, IIA and IIB.
Compounds of formulae I, IA and IB, in which R represents C(O)OR9, may be prepared by cyclisation of corresponding compounds of formulae VI, VIA and VIB, respectively: 
wherein R1, R3, R4 and X are as defined previously for compounds of formulae I, IA and IB, and R9alk represents an optionally substituted lower alkyl group, as defined hereinbefore, followed by removal of the alkyl group R9alk (if required) by hydrolysis and/or (if required) exchange with a further optionally substituted alkyl group.
Typically, the cyclisation reaction is accomplished using analogous methods to those previously described for compounds of formulae II, IIA and IIB.
Compounds of formulae VI, VIA and VIB may be prepared by reaction of corresponding compounds of formulae VII, VIIA and VIIB, respectively: 
wherein R1 and R9alk are as defined previously for compounds of formulae VI, VIA and VIB, with a compound of formula IV as defined hereinbefore. The reaction may be accomplished using analogous amide coupling conditions to those described previously in relation to compounds of formulae II, IIA and IIB.
Compounds of formulae I, IA and IB, in which R4 is, for example, lower alkoxycarbonyl (such as methoxycarbonyl), lower alkynyl (such as o acetylenyl), lower acyl (such as acetyl), Het or aryl, which latter four groups are optionally substituted, may be prepared by reaction of corresponding compounds of formulae VIII, VIIIA and VIIIB, respectively: 
wherein L is a leaving group, such as halo, preferably bromo or iodo, and R1, R2, R3 and X are as previously defined for compounds of formulae I, IA and IB, with a compound containing a group R4a which is capable of exchanging for L. R4a may be lower alkoxycarbonyl (such as methoxycarbonyl), lower alkynyl (such as acetylenyl), lower acyl (such as acetyl), Het, aryl (which latter four groups are optionally substituted), or, alternatively, R4a may be a group that is equivalent to (e.g. a tautomer of) any of the latter five groups. Conventional coupling chemistry, carbonylation chemistry or halogen metal exchange may be used in this reaction. In addition to the process conditions described in the processes hereinafter, suitable coupling conditions include:
(a) so-called xe2x80x9cSuzukixe2x80x9d conditions (e.g. 1.2 eq. of boronic acid, 2 eq. of K2CO3 and 0.1 eq. of Pd(PPh3)4, refluxing in an approximately 4:1 mixture of dioxane:water, or 2.5 to 3 eq. of CsF, 0.05 to 0.1 eq. of Pd2(dba)3 and 0.01 to 0.04 eq of P(o-tol)3, refluxing in DME);
(b) so-called xe2x80x9cStillexe2x80x9d conditions (e.g. 1.5 eq. of stannane, 10 eq. of LiCl, 0.15 eq. of CuI, and 0.1 eq. of Pd(PPh3)4, refluxing in dioxane, or 5 eq. of stannane, 3.6 eq. of Et3N, Pd2(dba) and P(o-tol)3, refluxing in MeCN);
(c) so-called xe2x80x9cHeckxe2x80x9d conditions (e.g. 2 eq. of a source of an acyl anion equivalent (such as butyl vinyl ether), 1.7 eq. of Et3N and catalytic amounts of Pd(OAc)2 and P(o-tol)3, in MeCN at between room temperature and reflux); or
(d) so-called xe2x80x9cSonogashiraxe2x80x9d conditions (for example as described in Synthesis 1980, 8, 627, such as 1.5 to 5 eq. of a terminal alkyne and 0.024 to 0.03 eq. of Pd(PPh3)2Cl2/CuI, in Et3N and MeCN at between room temperature and 60xc2x0 C.).
(e) Ni-catalysed conversion of an aryliodide to an S-linked isothiourea derivative which can be further transformed to a sulphoxide or a sulphone. Such conditions are described, for example, in Chemistry Letters, 1998, p 1979.
Suitable carbonylation conditions include reaction of a compound of formula VIII, VIIIA or VIIIB in which L represents halo with an appropriate palladium catalyst system (e.g. palladium(II) acetate combined with 1,2-bis(diphenylphosphino)propane (DPPP)) under an atmosphere of carbon monoxide (e.g. at a pressure of around 482.6 kPa (70 psi)) in the presence of an excess of a lower alkyl alcohol (e.g. methanol), an excess of a tertiary amine base (e.g. Et3N), and optionally in the presence of a suitable solvent (e.g. dimethylsulfoxide).
Group R4a may be a group R4, as defined in formulae I, IA and IB. Alternatively, R4a may be converted to a group R4 or to another group R4 using conventional chemical techniques. Examples of such conversions of groups R4a to R4 and interconversions of groups R4 are given in the Examples set out hereinafter.
Compounds of formula VIII, VIIIA and VIIIB may be prepared from corresponding compounds of formulae X, XA and XB, respectively: 
wherein R1, R2, R3 and X are as previously defined for compounds of formulae VIII, VIIIA and VIIIB, using methods known to those skilled in the art for converting an amino group to an L group, in which L is as previously defined for compounds of formulae VIII, VIIIA and VIIIB. L may be Hal, wherein Hal is iodo, bromo or chloro. For example, compounds of formulae VIII, VIIIA and VIIIB in which L is iodo may be prepared by lo reacting a corresponding compound of formula X, XA or XB with about a 4 to 5-fold excess of butyl nitrite in diiodomethane.
Compounds of formulae X, XA and XB may be prepared by cyclisation of corresponding compounds of formulae XI, XIA and XIB, respectively: 
wherein R1, R2, R3 and X are as previously defined for compounds of formulae X, XA and XB. This cyclisation may be carried out using similar techniques to those described hereinbefore for the preparation of compounds of formulae II, IIA and IIB, but it is preferably base mediated. Compounds of formulae XI, XIA and XIB may be prepared by the reduction of corresponding compounds of formulae XII, XIIA and XIIB, respectively: 
wherein R1, R2, R3 and X are as defined previously for compounds of formulae XI, XIA and XIB, by conventional techniques, such as catalytic hydrogenation. Typically, the hydrogenation may be achieved using a Raney(copyright) nickel catalyst in a suitable solvent such as ethanol at a hydrogen pressure of about 150 kPa to 500 kPa, especially 345 kPa, at from about 40xc2x0 C. to about 50xc2x0 C.
Compounds of formulae XII, XIIA and XIIB may be prepared by reaction of corresponding compounds of formulae II, IIIA and IIIB as defined hereinbefore, with a compound of formula XIII: 
wherein R3 and X are as previously defined for compounds of formulae XII, XIIA and XIIB. The reaction may be achieved using analogous amide bond forming techniques to those previously described for compounds of formulae II, IIA and IIB.
Compounds of formulae X, XA and XB may alternatively be prepared by reduction of corresponding compounds of formulae XIII, XIIIA and XIIIB, respectively: 
wherein R1, R2, R3 and X are as previously defined for compounds of formulae X, XA and XB. This reduction may be performed under a variety of reaction conditions, for example by catalytic hydrogenation (for example using: 10% Pd/C in an alcohol, such as ethanol, at 60 psi (415 kPa) H2 pressure and room temperature; or Raney(copyright) nickel in a suitable solvent such as ethanol at a hydrogen pressure of about 150 kPa to 500 kPa, especially 345 kPa, and at from about 40xc2x0 C. to about 50xc2x0 C.) or by transition metal catalysed reduction (e.g. at around room temperature in the presence of iron powder (e.g. 7 eq.) in acetic acid, or TiCl3 (e.g. 9 eq.) in acetic acid).
Compounds of formulae XIII, XIIIA and XIIIB may be prepared by reaction of a compound of formula XIIIC, 
or, preferably, a carboxylic acid addition salt thereof (e.g. an acetate or a formate), wherein X and R3 are as previously defined for compounds of formulae XIII, XIIIA and XIIIB, with either:
(a) a corresponding compound of formula III, IIIA or formula IIIB, as defined hereinbefore; or
(b) a corresponding compound of formula XVII, XVIIA or formula XVIIB, as defined hereinafter,
in both cases under conditions such as those described herein. Such reactions may be carried out, for example, using 1.0 to 1.1 equivalents of the amidine compound of formula XIIIC, for example by refluxing in 3-methyl-3-pentanol (e.g. for about 2.5 to 3 hours).
Compounds of formula XIIIC may be prepared from the corresponding cyanopyridine under conditions well known to those skilled in the art.
Compounds of formulae XIII, XIIIA and XIIIB in which R2 represents lower alkyl (which alkyl group is branched and unsaturated at the carbon atom that is attached to the rest of the molecule), lower alkoxycarbonyl, NR12R13, cyano, aryl or Het (which Het group is either aromatic or is unsaturated at the carbon atom that is attached to the rest of the molecule) may alternatively be prepared from corresponding compounds of formulae XIIID or XIIIE, respectively: 
wherein Hal represents Cl, Br or I, preferably I and especially Br, and R1, R3 and X are as previously defined for compounds of formulae XII, XIIIA and XIIIB, for example as described hereinafter for preparation of compounds of formulae I, IA and IB (see process 6 below). In addition to the process conditions described in process 6 below, suitable coupling conditions include:
(a) so-called xe2x80x9cSuzukixe2x80x9d conditions (e.g. 1.2 eq. of boronic acid, 2 eq. of K2CO3 and 0.1 eq. of Pd(PPh3)4, refluxing in an approximately 4:1 mixture of dioxane:water, or 2.5 to 3 eq. of CsF, 0.05 to 0.1 eq. of Pd2(dba)3 and 0.01 to 0.04 eq of P(o-tol)3, refluxing in DME);
(b) so-called xe2x80x9cStillexe2x80x9d conditions (e.g. 1.5 eq. of stannane, 10 eq. of LiCl, 0.15 eq. of CuI, and 0.1 eq. of Pd(PPh3)4, refluxing in dioxane, or 5 eq. of stannane, 3.6 eq. of Et3N, Pd2(dba) and P(o-tol)3, refluxing in MeCN);
(c) so-called xe2x80x9cHeckxe2x80x9d conditions (e.g. 2 eq. of a source of an acyl anion equivalent (such as butyl vinyl ether), 1.7 eq. of Et3N and catalytic amounts of Pd(OAc)2 and P(o-tol)3, in MeCN at between room temperature and reflux); or
(d) so-called xe2x80x9cSonogashiraxe2x80x9d conditions (for example as described in Synthesis 1980, 8, 627, such as 1.5 to 5 eq. of a terminal alkyne and 0.024 to 0.03 eq. of Pd(PPh3)2Cl2/CuI, in Et3N and MeCN at between room temperature and 60xc2x0 C.).
Suitable carbonylation conditions include reaction of a compound of formula XIIID or XIIIE with an appropriate palladium catalyst system (e.g. palladium(II) acetate combined with 1,2-bis(diphenylphosphino)-propane (DPPP)) under an atmosphere of carbon monoxide (e.g. at a pressure of around 482.6 kPa (70 psi)) in the presence of an excess of a lower alkyl alcohol (e.g. methanol), an excess of a tertiary amine base (e.g. Et3N), and optionally in the presence of a suitable solvent (e.g. dimethylsulfoxide).
Compounds of formula XIIID and XIIIE may be prepared by halogenation of corresponding compounds of formulae XIIIF and XIIIG, respectively: 
wherein R1, R3 and X are as hereinbefore defined, under conditions known to those skilled in the art (e.g., for bromination, at between room temperature and reflux in the presence of acetic acid as solvent, 1.5 to 2.0 eq. of bromine and e.g. 1.5 to 2.0 eq. of sodium acetate).
Compounds of formulae XIII, XIIIA and XIIIB may be prepared by coupling corresponding compounds of formulae XVII, XVIIA and XVIIB, respectively: 
wherein R1 and R2 are as previously defined for compounds of formulae XVI, XVIA and XVIB and R17 represents a lower (e.g. C1-6 alkyl) group, to with a compound of formula XIIIC.
5. Compounds of formulae I, IA and IB in which R1 represents lower alkyl, Het, aryl, alkylHet or alkylaryl (which latter five groups are all optionally substituted as defined hereinbefore in respect of R1) may be prepared by alkylation of corresponding compounds of formulae XXIIA or XXIIB, respectively (which the skilled person will appreciate are different tautomeric forms of the same compound): 
wherein R2, R3, R4 and X are as previously defined for compounds of formulae I, IA and IB, for example by reaction under conditions known to those skilled in the art with a compound of formula R1axe2x80x94L, wherein R1a represents lower alkyl, Het, aryl, alkylHet or alkylaryl (which latter five groups are all optionally substituted as defined hereinbefore in respect of R1) and L and Het are as hereinbefore defined. The skilled person will appreciate that compounds of formulae XXIIA and XXIIB are, respectively, compounds of formulae I, IA and IB in which R1 represents H.
Compounds of formulae XXIIA and XXIIB may be prepared by cyclisation of corresponding compounds of formulae XXIIIA and XXIIIB, respectively: 
wherein R2, R3, R4 and X are as hereinbefore defined, for example under conditions equivalent or analogous to those described hereinbefore in respect of the preparation of compounds of formulae I, IA and IB.
6. Compounds of formulae I, IA and IB, in which R2 represents optionally substituted lower alkyl (which alkyl group is branched and unsaturated at the carbon atom that is attached to the rest of the molecule), NR12R13, cyano, aryl or Het (which Het group is either aromatic or unsaturated at the carbon atom that is attached to the rest of the molecule), may be prepared by cross-coupling of corresponding compounds of formula XXIV, XXIVA and XXIVB: 
wherein Hal, R1, R3, R4 and X are as hereinbefore defined, using a compound of formula
R2aM
wherein R2a represents optionally substituted lower alkyl (which alkyl group is branched and unsaturated at the carbon atom that is attached to M), NR12R13, cyano, aryl or Het (which Het group is either aromatic or unsaturated at the carbon atom that is attached to M), R12 and R13 are as hereinbefore defined and M represents an optionally substituted metal or boron group, which group is suitable for cross-coupling reactions, for example a trialkylstannane (e.g. tri-n-butylstannane), a dialkylborane (e.g. diethylborane), a dialkoxy borane, a dihydroxyborane, lithium, a halomagnesium, a halozinc, copper, a halomercury, in the presence of an appropriate catalyst system (e.g. a palladium or nickel catalyst).
The cross-coupling reaction is preferably carried out in the presence of a base (e.g. potassium carbonate, cesium fluoride or triethylamine), preferably in excess. Those skilled in the art will appreciate that the type of catalyst that is employed will depend on factors such as the nature of the M group, the substrate that is employed etc.
Typical procedures that may be employed include those described hereinafter. In a further typical procedure, a compound of formula R2aM may be used, in which M is halozinc. Such a compound may be prepared by reaction of a compound R2Hal, where Hal and R2 are as hereinbefore defined, with an alkyllithium (e.g. n-butyllithium) at a temperature of between xe2x88x9278xc2x0 C. and room temperature, in a suitable solvent (e.g. THF), and the resultant solution is then treated with Zn(II)Cl2 (solution in ether) and the resultant solution is treated with a compound of formula XXIV, XXIVA or XXIVB in the presence of a palladium catalyst (e.g. tetrakis(triphenyl-phosphine)palladium(0)) in a suitable solvent (e.g. THF). The reaction may be carried out at from room temperature to reflux temperature.
Suitable coupling conditions also include so-called Suzuki and Stille conditions such as those described hereinbefore in respect of preparation of compounds of formulae XXIII, XIIIA and XIIIB,
The skilled person will appreciate that compounds of formulae I, IA and IB in which R2 represents lower alkyl that is branched, but not unsaturated, at the carbon atom that is attached to the rest of the molecule may be prepared by in this way, provided that the corresponding compound of formula I, IA or IB in which the corresponding R2 group is unsaturated is subsequently hydrogenated under conditions known to those skilled in the art.
Compounds of formulae XXIV, XXIVA and XXIVB may be prepared by cyclisation of corresponding compounds of formulae XXV, XXVA and XXVB, respectively: 
in which R1, R3, R4, X and Hal are as hereinbefore defined, for example under analogous reaction conditions to those described hereinbefore for compounds of formulae II, IIA and IIB.
Compounds of formulae XXV, XXVA and XXVB may be prepared analogously to methods described herein, for example coupling of a compound of formula IV, as hereinbefore defined, to an appropriate 4-amino-3-halopyrazole-5-carboxamide, which pyrazole compound may, in turn, be prepared by halogenation of a corresponding 4-aminopyrazole-5-carboxamide, under conditions which are well known to those skilled in the art.
Compounds of formulae XXIV, XXIVA and XXIVB may alternatively be prepared from corresponding compounds of formulae XXVI, XXVIA and XXVIB, respectively: 
wherein X, Hal, R1 and R3 are as hereinbefore defined, for example as described hereinbefore for preparation of compounds of formulae I, IA and IB from compounds of formulae X, XA and XB (via compounds of formulae VIII, VIIIA and VIIIB; see process 4 above).
Compounds of formulae XXVI, XXVIA and XXVIB may be prepared via routine techniques (for example, reduction of corresponding nitropyridine compounds of formulae XIIID and XIIIE as defined herein, respectively, using for example the methods for the reduction of compounds of formulae XXII, XIIA and XIIB as described herein).
7. Compounds of formulae I, IA and IB in which R2 represents lower acyl (e.g. acetyl), lower alkoxycarbonyl (e.g. methoxycarbonyl) or lower alkynyl may be prepared by a cross-coupling reaction between corresponding compounds of formulae XXIV, XXIVA and XXIVB, respectively, as defined above, and a reagent or reagents capable of delivering the lower acyl, lower alkoxycarbonyl or lower alkynyl group (or groups equivalent to (e.g. tautomers of) these). Suitable cross-coupling conditions include the Heck, Sonogashira and palladium-catalysed carbonylation conditions described at process 4 above.
Compounds of formulae III, IIIA and IIIB, IV, VII, VIIA and VIIB, XIII, XIIIF and XIIIG, XXIII, XXIIIA and XXIIIB, compounds of formulae HNR12R13, R2aM, R3OH, and R1axe2x80x94L, other compounds mentioned hereinbefore, and derivatives thereof, when not commercially available or not subsequently described, may be obtained either by analogy with the processes described hereinbefore, or by conventional synthetic procedures, in accordance with standard techniques, from readily available starting materials using appropriate reagents and reaction conditions.
Substituents on the aryl and Het groups in the above-mentioned compounds may be introduced, and interconverted, using techniques which are well known to those skilled in the art.
The skilled person will also appreciate that various standard substituent or functional group interconversions and transformations within certain compounds of formulae I, IA and IB will provide other compounds of formulae I, IA and IB. For example, when X is NR5, the compounds of formulae I, IA and IB in which X is O may be treated with an excess of R3R5NH, or a suitable acid addition salt thereof, in the presence of an excess of a sterically hindered amine in a suitable solvent. Typically, R3R5NH is used as the free base with about a 3-fold excess (over the substrate) of potassium bis(trimethylsilyl)amide (KHMDS) in dimethylformamide (DMF) as solvent at about 100xc2x0 C. Alternatively, an excess of R3R5NH may be used as the solvent and the reaction conducted in the presence of about a 50% excess of copper(II) sulfate at up to the reflux temperature of the reaction medium. Where the desired amino substituent on the compound of the formula I, IA or IB is xe2x80x94NR3R5and one of either R3 or R5 is H, then the exchange reaction may be carried out by refluxing with the appropriate amine, a copper(II) sulfate penta- or hepta-hydrate or KHDMS in DMF. Typically, to exchange the OR3 group for alternative amines of the formula NHR3R5, such as compounds wherein R3 or R5 are selected from aliphatic or cyclic amines, optionally including oxygen, then the reaction is preferably carried out by treating with the appropriate amine and about 8 equivalents of potassium bis(trimethylsilyl)amide in DMF for about 18 hours at 100xc2x0 C. Further examples when X is O include alkoxide exchange at the 2-position of the pyridin-3-yl substituents, and for compounds in which one or more of R1, R2, R3 and/or R4 represents an alkyl group which is terminated by OH, deprotection of a corresponding ether compound of formula I, IA or IB (see the Examples below). Moreover, certain compounds of formulae I, IA and IB, for example those in which R12 and R13, together with the nitrogen to which they are attached, form a 4-lower alkyl-piperazinyl group, may be prepared directly from the corresponding piperazine analogues, using standard procedures (e.g. alkylation).
Further standard substituent or functional group interconversions and transformations that may be performed on compounds of formulae I, IA and IB include procedures described hereinafter. In this respect:
(i) alkoxycarbonyl may be hydrolysed to carboxy under acidic or basic conditions;
(ii) amino may be alkylated (either by reaction with an alkylating agent or by reductive alkylation) to give alkylamino or dialkylamino;
(iii) amino may be acylated to give acylamino or sulfonated to give sulfonylamino or disulfonylamino;
(iv) disulfonylamino may be hydrolysed to sulfonylamino under basic conditions;
(v) alkynyl may be hydrolysed to acyl in the presence of a catalyst such as a mercury(II) salt;
(vi) alkynyl may be oxidised to xcex1-hydroxy acyl in the presence of an oxidising agent such as a phenyliodine(III) bis(trifluoroacetate), for example as described in Tet. Lett. 1985, 26, 3837;
(vii) hydroxy may be converted to halo by reaction with a halogenating agent;
(viii) halo may be converted to cyano by reaction with a metal cyanide salt (e.g. Cu(I) cyanide); and
(ix) enolisable acyl groups may be converted to xcex2-amino acyl by reaction with an aldehyde and an amine under xe2x80x9cso calledxe2x80x9d Mannich conditions.
In addition, certain acyclic groups may be converted to certain heterocyclic groups using reagents and conditions known to those skilled in the art, for example as described in Comprehensive Heterocyclic Chemistry II, edited by A R Katritsky, C W Rees and E F V Scriven, 1st Edition, Elsevier Science Ltd., Volumes 1-11 (1996).
The compounds of the invention may be isolated from their reaction mixtures using conventional techniques.
It will be appreciated by those skilled in the art that, in the course of carrying out the above processes described above, the functional groups of intermediate compounds may need to be protected by protecting groups.
Functional groups which it is desirable to protect include hydroxy, amino and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl and diarylalkylsilyl groups (e.g. tert-butyldimethylsilyl, tert-butyldiphenylsilyl or trimethylsilyl) and tetrahydropyranyl. Suitable protecting groups for amino include tert-butyloxycarbonyl, 9-fluorenyl-methoxycarbonyl or benzyloxycarbonyl. Suitable protecting groups for carboxylic acid include C1-6 alkyl or benzyl esters.
The protection and deprotection of functional groups may take place before or after any of the reaction steps described hereinbefore.
Protecting groups may be removed in accordance with techniques which are well known to those skilled in the art.
The use of protecting groups is fully described in xe2x80x9cProtective Groups in Organic Chemistryxe2x80x9d, edited by J W F McOmie, Plenum Press (1973), and xe2x80x9cProtective Groups in Organic Synthesisxe2x80x9d, 2nd edition, T W Greene and P G M Wutz, Wiley-Interscience (1991).
Persons skilled in the art will also appreciate that, in order to obtain compounds of formula I, or IA or IB, in an alternative, and, on some occasions, more convenient, manner, the individual process steps mentioned hereinbefore may be performed in a different order, and/or the individual reactions may be performed at a different stage in the overall route (i.e. substituents may be added to and/or chemical transformations performed upon, different intermediates to those mentioned hereinbefore in conjunction with a particular reaction). This will depend inter alia on factors such as the nature of other functional groups present in a particular substrate, the availability of key intermediates and the protecting group strategy (if any) to be adopted. Clearly, the type of chemistry involved will influence the choice of reagent that is used in the said synthetic steps, the need, and type, of protecting groups that are employed, and the sequence for accomplishing the synthesis.
Pharmaceutically acceptable acid addition salts of the compounds of formulae I, IA and IB which contain a basic centre may be prepared in a conventional manner. For example, a solution of the free base may be treated with the appropriate acid, either neat or in a suitable solvent, and the resulting salt may then be isolated either by filtration of by evaporation under vacuum of the reaction solvent. Pharmaceutically acceptable base addition salts can be obtained in an analogous manner by treating a solution of a compound of formula I, IA or IB with the appropriate base. Both types of salt may be formed or interconverted using ion-exchange resin techniques.
The present invention also includes all suitable isotopic variations of a compound of the formula (I) or a pharmaceutically acceptable salt thereof. An isotopic variation of a compound of the formula (I) or a pharmaceutically acceptable salt thereof is defined as one in which at least one atom is replaced by an atom having the same atomic number but an atomic mass different from the atomic mass usually found in nature. Examples of isotopes that can be incorporated into compounds of the formula (I) and pharmaceutically acceptable salts thereof include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulphur, fluorine and chlorine such as 2H, 3H, 13C, 14C, 15N, 17O, 18O, 31P, 32P, 35S, 18F and 36Cl, respectively. Certain isotopic variations of the compounds of the formula (I) and pharmaceutically acceptable salts thereof, for example, those in which a radioactive isotope such as 3H or 14C is incorporated, are useful in drug and/or substrate tissue distribution studies. Tritiated, i.e., 3H, and carbon-14, i.e., 14C, isotopes are particularly preferred for their ease of preparation and detectability. Further, substitution with isotopes such as deuterium, i.e., 2H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements and hence may be preferred in some circumstances. Isotopic variations of the compounds of formula (I) and pharmaceutically acceptable salts thereof of this invention can generally be prepared by conventional procedures such as by the illustrative methods or by the preparations described in the Examples and Preparations hereafter using appropriate isotopic variations of suitable reagents.
It will be appreciated by those skilled in the art that certain protected derivatives of compounds of formula I, which may be made prior to a final deprotection stage, may not possess pharmacological activity as such, but may, in certain instances, be administered orally or parenterally and thereafter metabolised in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as xe2x80x9cprodrugsxe2x80x9d. Further, certain compounds of formula I may act as prodrugs of other compounds of formula I.
All protected derivatives, and prodrugs, of compounds of formula I are included within the scope of the invention.
The present invention additionally comprises the combination of a cGMP PDE5 inhibitor compound of the general formula (I), wherein said combination can be administered by sequential, simultaneous or joint administration of a compound of general formula (I) with:
(a) one or more naturally occurring or synthetic prostaglandins or esters thereof. Suitable prostaglandins for use herein include compounds such as alprostadil, prostaglandin E1, prostaglandin E0, 13, 14-dihydroprosta glandin E1, prostaglandin E2, eprostinol, natural synthetic and semi-synthetic prostaglandins and derivatives thereof including those described in U.S. Pat. No. 6,037,346 issued on Mar. 14th, 2000 and incorporated herein by reference, PGE0, PGE1, PGA1, PGB1, PGF1xcex1, 19-hydroxy PGA1, 19-hydroxy-PGB1, PGE2, PGB2, 19-hydroxy-PGA2, 19-hydroxy-PGB2, PGE3xcex1, carboprost tromethamine dinoprost, tromethamine, dinoprostone, lipo prost, gemeprost, metenoprost, sulprostune, tiaprost and moxisylate; and/or
(b) one or more xcex1-adrenergic receptor antagonist compounds also known as xcex1-adrenoceptors or xcex1-receptors or xcex1-blockers. Suitable compounds for use herein include: the xcex1-adrenergic receptors as described in PCT application WO99/30697 published on June 14th, 1998, the disclosures of which relating to xcex1-adrenergic receptors are incorporated herein by reference and include, selective xcex11-adrenoceptors or xcex12-adrenoceptors and non-selective adrenoceptors, suitable xcex11-adrenoceptors include: phentolamine, phentolamine mesylate, trazodone, alfuzosin, indoramin, naftopidil, tamsulosin, dapiprazole, phenoxybenzamine, idazoxan, efaraxan, yohimbine, rauwolfa alkaloids, Recordati 15/2739, SNAP 1069, SNAP 5089, RS17053, SL 89.0591, doxazosin, terazosin, abanoquil and prazosin; xcex12-blockers from U.S. Pat. No. 6,037,346 [Mar. 14th, 2000] dibenamine, tolazoline, trimazosin and dibenamine; xcex1-adrenergic receptors as described in US Pat. Nos. 4,188,390; 4,026,894; 3,511,836; 4,315,007; 3,527,761; 3,997,666; 2,503,059; 4,703,063; 3,381,009; 4,252,721 and 2,599,000 each of which is incorporated herein by reference; xcex12-Adrenoceptors include: clonidine, papaverine, papaverine hydrochloride, optionally in the presence of a cariotonic agent such as pirxamine; and/or
(c) one or more NO-donor (NO-agonist) compounds. Suitable NO-donor compounds for use herein include organic nitrates, such as mono- di or tri-nitrates or organic nitrate esters including glyceryl brinitrate (also known as nitroglycerin), isosorbide 5-mononitrate, isosorbide dinitrate, pentaerythritol tetranitrate, erythrityl tetranitrate, sodium nitroprusside (SNP), 3-morpholinosydnonimine molsidomine, S-nitroso-N-acetyl penicilliamine (SNAP) S-nitroso-N-glutathione (SNO-GLU), N-hydroxy-L-arginine, amylnitrate, linsidomine, linsidomine chlorohydrate, (SIN-1) S-nitroso-N-cysteine, diazenium diolates, (NONOates), 1,5-pentanedinitrate, L-arginene, ginseng, zizphi fructus, molsidomine, Re-2047, nitrosylated maxisylyte derivatives such as NMI-678-11 and NMI-937 as described in published PCT application WO 0012075; and/or
(d) one or more potassium channel openers. Suitable potassium channel openers for use herein include nicorandil, cromokalim, levcromakalim, lemakalim, pinacidil, cliazoxide, minoxidil, charybdotoxin, glyburide, 4-amini pyridine, BaCl2; and/or
(e) one or more dopaminergic agents. Suitable dopaminergic compounds for use herein include D2-agonists such as, pramipexol; apomorphine; and/or
(f) one or more vasodilator agents. Suitable vasodilator agents for use herein include nimodepine, pinacidil, cyclandelate, isoxsuprine, chloroprumazine, halo peridol, Rec 15/2739, trazodone, pentoxifylline; and/or
(g) one or more thromboxane A2 agonists; and/or
(h) one or more CNS active agents; and/or
(i) one or more ergot alkoloids; Suitable ergot alkaloids are described in U.S. Pat. No. 6,037,346 issued on Mar. 14th, 2000 and include acetergamine, brazergoline, bromerguride, cianergoline, delorgotrile, disulergine, ergonovine maleate, ergotamine tartrate, etisulergine, lergotrile, lysergide, mesulergine, metergoline, metergotamine, nicergoline, pergolide, propisergide, proterguride, terguride; and/or
(k) one or more compounds which modulate the action of atrial natruretic factor (also known as atrial naturetic peptide), such as inhibitors or neutral endopeptidase; and/or
(l) one or more compounds which inhibit angiotensin-converting enzyme such as enapril, and combined inhibitors of angiotensin-converting enzyme and neutral endopeptidase such as omapatrilat; and/or
(m) one or more angiotensin receptor antagonists such as losartan; and/or
(n) one or more substrates for NO-synthase, such as L-arginine; and/or
(o) one or more calcium channel blockers such as amlodipine; and/or
(p) one or more antagonists of endothelin receptors and inhibitors or endothelin-converting enzyme; and/or
(q) one or more cholesterol lowering agents such as statins and fibrates; and/or
(r) one or more antiplatelet and antithrombotic agents, e.g. tPA, uPA, warfarin, hirudin and other thrombin inhibitors, heparin, thromboplastin activating factor inhibitors; and/or
(s) one or more insulin sensitising agents such as rezulin and hypoglycaemic agents such as glipizide; and/or
(t) L-DOPA or carbidopa; and/or
(u) one or more acetylcholinesterase inhibitors such as donezipil; and/or
(v) one or more steroidal or non-steroidal anti-inflammatory agents.
The compounds of the invention are useful because they possess pharmacological activity in animals, especially mammals, including humans. They are therefore indicated as pharmaceuticals, as well as for use as animal medicaments.
According to a further aspect of the invention there is provided the compounds of the invention for use as pharmaceuticals, and for use as animal medicaments.
In particular, compounds of the invention have been found to be potent and selective inhibitors of cGMP PDEs, such as cGMP PDE5, for example as demonstrated in the tests described below, and are thus useful in the treatment of medical conditions in humans, and in animals, in which cGMP PDEs, such as cGMP PDE5, are indicated, and in which inhibition of cGMP PDEs, such as cGMP PDE5, is desirable.
By the term xe2x80x9ctreatmentxe2x80x9d, we include both therapeutic (curative), palliative or prophylactic treatment.
Thus, according to a further aspect of the invention there is provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of a medical condition in which a cGMP PDE (e.g. cGMP PDE5) is indicated. There is further provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of a medical condition in which inhibition of a cGMP PDE (e.g. cGMP PDE5) is desirable.
The compounds of the invention are thus expected to be useful for the curative, palliative or prophylactic treatment of mammalian sexual disorders. In particular, the compounds are of value in the treatment of mammalian sexual dysfunctions such as male erectile dysfunction (MED), impotence, female sexual dysfunction (FSD), clitoral dysfunction, female hypoactive sexual desire disorder, female sexual arousal disorder, female sexual pain disorder or female sexual orgasmic dysfunction (FSOD) as well as sexual dysfunction due to spinal cord injury or selective serotonin re-uptake inhibitor (SSRI) induced sexual dysfunction but, clearly, will be useful also for treating other medical conditions for which a potent and selective cGMP PDE5 inhibitor is indicated. Such conditions include premature labour, dysmenorrhoea, benign prostatic hyperplasia (BPH), bladder outlet obstruction, incontinence, stable, unstable and variant (Prinzmetal) angina, hypertension, pulmonary hypertension, chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, atherosclerosis, conditions of reduced blood vessel patency, e.g. post-percutaneous transluminal coronary angioplasty (post-PTCA), peripheral vascular disease, stroke, nitrate induced tolerance, bronchitis, allergic asthma, chronic asthma, allergic rhinitis, diseases and conditions of the eye such as glaucoma, optic neuropathy, macular degeneration, elevated intra-occular pressure, retinal or arterial occulsion and diseases characterised by disorders of gut motility, e.g. irritable bowel syndrome (IBS).
Further medical conditions for which a potent and selective cGMP PDE5 inhibitor is indicated, and for which treatment with compounds of the present invention may be useful include pre-eclampsia, Kawasaki""s syndrome, nitrate tolerance, multiple sclerosis, diabetic nephropathy, neuropathy including autonomic and peripheral neuropathy and in particular diabetic neuropathy and symptoms thereof e.g. gastroparesis, peripheral diabetic neuropathy, Alzheimer""s disease, acute respiratory failure, psoriasis, skin necrosis, cancer, metastasis, baldness, nutcracker oesophagus, anal fissure, haemorrhoids, hypoxic vasoconstriction as well as the stabilisation of blood pressure during haemodialysis.
Particularly preferred conditions include MED and FSD.
Thus, the invention provides a method of treating or preventing a medical condition for which a cGMP PDE5 inhibitor is indicated, in an animal (e.g. a mammal, including a human being), which comprises administering a therapeutically effective amount of a compound of the invention to a mammal in need of such treatment.
The compounds of the invention will normally be administered orally or by any parenteral route, in the form of pharmaceutical preparations comprising the active ingredient, optionally in the form of a non-toxic organic, or inorganic, acid, or base, addition salt, in a pharmaceutically acceptable dosage form. Depending upon the disorder and patient to be treated, as well as the route of administration, the compositions may be administered at varying doses.
The compounds of the invention may also be combined with any other drugs useful in the inhibition of cGMP-PDEs, such as cGMP-PDE5.
The compounds of the invention, their pharmaceutically acceptable salts, and pharmaceutically acceptable solvates of either entity can be administered alone but, in human therapy will generally be administered in admixture with a suitable pharmaceutical excipient diluent or carrier selected with regard to the intended route of administration and standard pharmaceutical practice.
For example, the compounds of the invention or salts or solvates hereof can be administered orally, buccally or sublingually in the form of tablets, capsules (including soft gel capsules), ovules, elixirs, solutions or suspensions, which may contain flavouring or colouring agents, for immediate-, delayed-, modified-, or controlled-release such as sustained-, dual-, or pulsatile delivery applications. The compounds of the invention may also be administered via intracavernosal injection. The compounds of the invention may also be administered via fast dispersing or fast dissolving dosages forms or in the form of a high energy dispersion or as coated particles. Suitable pharmaceutical formulations of the compounds of the invention may be in coated or un-coated form as desired.
Such tablets may contain excipients such as microcrystalline cellulose, lactose, sodium citrate, calcium carbonate, dibasic calcium phosphate, glycine and starch (preferably corn, potato or tapioca starch), disintegrants such as sodium starch glycollate, croscarmellose sodium and certain complex silicates, and granulation binders such as polyvinylpyrrolidone, hydroxypropylmethyl cellulose (HPMC), hydroxypropylcellulose (HPC), sucrose, gelatin and acacia. Additionally, lubricating agents such as magnesium stearate, stearic acid, glyceryl behenate and talc may be included.
Solid compositions of a similar type may also be employed as fillers in gelatin capsules. Preferred excipients in this regard include lactose, starch, a cellulose, milk sugar or high molecular weight polyethylene glycols. For aqueous suspensions and/or elixirs, the compounds of the invention may be combined with various sweetening or flavouring agents, colouring matter or dyes, with emulsifying and/or suspending agents and with diluents such as water, ethanol, propylene glycol and glycerin, and combinations thereof.
Modified release and pulsatile release dosage forms may contain excipients such as those detailed for immediate release dosage forms together with additional excipients that act as release rate modifiers, these being coated on and/or included in the body of the device. Release rate modifiers include, but are not exclusively limited to, hydroxypropylmethyl cellulose, methyl cellulose, sodium carboxymethylcellulose, ethyl cellulose, cellulose acetate, polyethylene oxide, Xanthan gum, Carbomer, ammonio methacrylate copolymer, hydrogenated castor oil, carnauba wax, paraffin wax, cellulose acetate phthalate, hydroxypropylmethyl cellulose phthalate, methacrylic acid copolymer and mixtures thereof. Modified release and pulsatile release dosage forms may contain one or a combination of release rate modifying excipients. Release rate modifying excipients maybe present both within the dosage form i.e. within the matrix, and/or on the dosage form i.e. upon the surface or coating.
Fast dispersing or dissolving dosage formulations (FDDFs) may contain the following ingredients: aspartame, acesulfame potassium, citric acid, croscarmellose sodium, crospovidone, diascorbic acid, ethyl acrylate, ethyl cellulose, gelatin, hydroxypropylmethyl cellulose, magnesium stearate, mannitol, methyl methacrylate, mint flavouring, polyethylene glycol, fumed silica, silicon dioxide, sodium starch glycolate, sodium stearyl fumarate, sorbitol, xylitol. The terms dispersing or dissolving as used herein to describe FDDFs are dependent upon the solubility of the drug substance used i.e. where the drug substance is insoluble a fast dispersing dosage form can be prepared and where the drug substance is soluble a fast dissolving dosage form can be prepared.
The compounds of the invention can also be administered parenterally, for example, intracavernosally, intravenously, intra-arterially, intraperitoneally, intrathecally, intraventricularly, intraurethrally intrasternally, intracranially, intramuscularly or subcutaneously, or they may be administered by infusion or needless injection techniques. For such parenteral administration they are best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood. The aqueous solutions should be suitably buffered (preferably to a pH of from 3 to 9), if necessary. The preparation of suitable parenteral formulations under sterile conditions is readily accomplished by standard pharmaceutical techniques well-known to those skilled in the art.
For oral and parenteral administration to human patients, the daily dosage level of the compounds of the invention or salts or solvates thereof will usually be from 10 to 500 mg (in single or divided doses).
Thus, for example, tablets or capsules of the compounds of the invention or salts or solvates thereof may contain from 5mg to 250 mg of active compound for administration singly or two or more at a time, as appropriate. The physician in any event will determine the actual dosage which will be most suitable for any individual patient and it will vary with the age, weight and response of the particular patient. The above dosages are exemplary of the average case. There can, of course, be individual instances where higher or lower dosage ranges are merited and such are within the scope of this invention. The skilled person will also appreciate that, in the treatment of certain conditions (including MED and FSD), compounds of the invention may be taken as a single dose on an xe2x80x9cas requiredxe2x80x9d basis (i.e. as needed or desired).
In general a tablet formulation could typically contain between about 0.01 mg and 500 mg of a compound according to the present invention (or a salt thereof) whilst tablet fill weights may range from 50 mg to 1000 mg. An example formulation for a 10 mg tablet is illustrated:
Such tablets can be manufactured by standard processes, for example, direct compression or a wet or dry granulation process. The tablet cores may be coated with appropriate overcoats.
The compounds of the invention can also be administered intranasally or by inhalation and are conveniently delivered in the form of a dry powder inhaler or an aerosol spray presentation from a pressurised container, pump, spray or nebuliser with the use of a suitable propellant, e.g. dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, a hydrofluoroalkane such as 1,1,1,2-tetrafluoroethane (HFA 134A [trade mark] or 1,1,1,2,3,3,3-heptafluoropropane (HFA 227EA [trade mark]), carbon dioxide or other suitable gas. In the case of a pressurised aerosol, the dosage unit may be determined by providing a valve to deliver a metered amount. The pressurised container, pump, spray or nebuliser may contain a solution or suspension of the active compound, e.g. using a mixture of ethanol and the propellant as the solvent, which may additionally contain a lubricant, e.g. sorbitan trioleate. Capsules and cartridges (made, for example, from gelatin) for use in an inhaler or insufflator may be formulated to contain a powder mix of a compound of the invention and a suitable powder base such as lactose or starch.
Aerosol or dry powder formulations are preferably arranged so that each metered dose or xe2x80x9cpuffxe2x80x9d contains from 1 to 50 mg of a compound of the invention for delivery to the patient. The overall daily dose with an aerosol will be in the range of from 1 to 50 mg which may be administered in a single dose or, more usually, in divided doses throughout the day.
The compounds of the invention may also be formulated for delivery via an atomiser. Formulations for atomiser devices may contain the following ingredients as solubilisers, emulsifiers or suspending agents: water, ethanol, glycerol, propylene glycol, low molecular weight polyethylene glycols, sodium chloride, fluorocarbons, polyethylene glycol ethers, sorbitan trioleate, oleic acid.
Alternatively, the compounds of the invention or salts or solvates thereof can be administered in the form of a suppository or pessary, or they may be applied topically in the form of a gel, hydrogel, lotion, solution, cream, ointment or dusting powder. The compounds of the invention or salts or solvates thereof may also be dermally administered. The compounds of the invention or salts or solvates thereof may also be transdermally administered, for example, by the use of a skin patch. They may also be administered by the ocular, pulmonary or rectal routes.
For ophthalmic use, the compounds can be formulated as micronised suspensions in isotonic, pH adjusted, sterile saline, or, preferably, as solutions in isotonic, pH adjusted, sterile saline, optionally in combination with a preservative such as a benzylalkonium chloride. Alternatively, they may be formulated in an ointment such as petrolatum.
For application topically to the skin, the compounds of the invention or salts or solvates thereof can be formulated as a suitable ointment containing the active compound suspended or dissolved in, for example, a mixture with one or more of the following: mineral oil, liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylene polyoxypropylene compound, emulsifying wax and water. Alternatively, they can be formulated as a suitable lotion or cream, suspended or dissolved in, for example, a mixture of one or more of the following: mineral oil, sorbitan monostearate, a polyethylene glycol, liquid paraffin, polysorbate 60, cetyl esters wax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol and water.
The compounds of the invention may also be used in combination with a cyclodextrin. Cyclodextrins are known to form inclusion and non-inclusion complexes with drug molecules. Formation of a drug-cyclodextrin complex may modify the solubility, dissolution rate, bioavailability and/or stability property of a drug molecule. Drug-cyclodextrin complexes are generally useful for most dosage forms and administration routes. As an alternative to direct complexation with the drug the cyclodextrin may be used as an auxiliary additive, e.g. as a carrier, diluent or solubiliser. Alpha-, beta- and gamma-cyclodextrins are most commonly used and suitable examples are described in WO-A-91/11172, WO-A-94/02518 and WO-A-98/55148.
Generally, in humans, oral administration of the compounds of the invention is the preferred route, being the most convenient and, for example in MED, avoiding the well-known disadvantages associated with intracavernosal (i.c.) administration. A preferred oral dosing regimen in MED for a typical man is from 25 to 250 mg of compound when required. In circumstances where the recipient suffers from a swallowing disorder or from impairment of drug absorption after oral administration, the drug may be administered parenterally, sublingually or buccally.
For veterinary use, a compound of the invention, or a veterinarily acceptable salt thereof, or a veterinarily acceptable solvate or pro-drug thereof, is administered as a suitably acceptable formulation in accordance with normal veterinary practice and the veterinary surgeon will determine the dosing regimen and route of administration which will be most appropriate for a particular animal.
Thus, according to a further aspect of the invention there is provided a pharmaceutical formulation including a compound of the invention in admixture with a pharmaceutically or veterinarily acceptable adjuvant, diluent or carrier.
In addition to the fact that compounds of the invention inhibit cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDES) and in particular, are potent and selective inhibitors of cGMP PDE5, compounds of the invention may also have the advantage that they may be more efficacious than, be less toxic than, have a broader range of activity than, be more potent than, produce fewer side effects than, be more easily absorbed than, or they may have other useful pharmacological properties over, compounds known in the prior art.
The biological activities of the compounds of the present invention were determined by the following test methods.
The compounds of the present invention are potent and selective cGMP PDE5 inhibitors. In vitro PDE inhibitory activities against cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate (cGMP) and cyclic adenosine 3xe2x80x2,5xe2x80x2-monophosphate (cAMP) phosphodiesterases were determined by measurement of their IC50 values (the concentration of compound required for 50% inhibition of enzyme activity).
The required PDE enzymes were isolated from a variety of sources, including human corpus cavernosum, human and rabbit platelets, human cardiac ventricle, human skeletal muscle and bovine retina, essentially by the method of W. J. Thompson and M. M. Appleman (Biochem., 1971, 10, 311). In particular, the cGMP-specific PDE (PDE5) and the cGMP-inhibited cAMP PDE (PDE3) were obtained from human corpus cavernosum tissue, human platelets or rabbit platelets; the cGMP-stimulated PDE (PDE2) was obtained from human corpus cavernosum; the calcium/calmodulin (Ca/CAM)-dependent PDE (PDEL) from human cardiac ventricle; the cAMP-specific PDE (PDE4) from human skeletal muscle; and the photoreceptor PDE (PDE6) from bovine retina. Phosphodiesterases 7-11 were generated from full length human recombinant clones transfected into SF9 cells.
Assays were performed either using a modification of the xe2x80x9cbatchxe2x80x9d method of W. J. Thompson et al. (Biochem., 1979, 18, 5228) or using a scintillation proximity assay for the direct detection of AMP/GMP using a modification of the protocol described by Amersham plc under product code TRKQ7090/7100. In summary, the effect of PDE inhibitors was investigated by assaying a fixed amount of enzyme in the presence of varying inhibitor concentrations and low substrate, (cGMP or cAMP in a 3:1 ratio unlabelled to [3H]-labeled at a conc xcx9c1/3 Km) such that IC50≅Ki. The final assay volume was made up to 100 xcexcl with assay buffer [20 mM Tris-HCl pH 7.4, 5 mM MgCl2, 1 mg/ml bovine serum albumin]. Reactions were initiated with enzyme, incubated for 30-60 min at 30xc2x0 C. to give  less than 30% substrate turnover and terminated with 50 xcexcl yttrium silicate SPA beads (containing 3 mM of the respective unlabelled cyclic nucleotide for PDEs 9 and 11). Plates were re-sealed and shaken for 20 min, after which the beads were allowed to settle for 30 min in the dark and then counted on a TopCount plate reader (Packard, Meriden, Conn.) Radioactivity units were converted to % activity of an uninhibited control (100%), plotted against inhibitor concentration and inhibitor IC50 values obtained using the xe2x80x98Fit Curvexe2x80x99 Microsoft Excel extension. Results from these tests show that the compounds of the present invention are potent and selective inhibitors of cGMP-specific PDE5.
Preferred compounds of the present invention, such as those of Examples 1, 20, 22, 24, 32, 34, 44a, 44b, 44c, 63, 64, 65, 66, 67, and 85 and the compounds of Examples 5, 16, 17, 21, 26, 29, 47, 48, 49, 50, 50a, 51, 51a, 59, 68, 70, 71, 73, 74, 75, 77, 79, 80, 84, 86, 87, 89, 91, 92, 113, 114, 116, 118-128, 130-136, 138, 140, 143 have IC50 values of less than about 10 nM for the PDE5 enzyme. A further preferred group of compounds having IC50 values of less than about 10 nM for the PDE5 enzyme, are those of Examples 48, 50, 51, 51a, 59, 113, 114, 116, 118, 119, 121, 122-129, 131-136, 138, 140, 143. An additional group of compounds, such as those of Examples 48, 50, 51, 51a, 59, 63, 65, 70, 71, 72, 73, 76, 77, 78, 79, 80, 81, 82, 83, 89, 91, 92, 94, 113, 114, 116, 122-127, 129, 131, 132, 133, 134, 138, 140 have IC50 values of less than about 5 nM for the PDE5 enzyme.
Especially preferred herein are compounds which have an IC50 value of less than about 10, more preferably less than about 5 nM for the PDE5 enzyme in combination with greater than 10-fold selectivity for the PDE5 enzyme versus the PDE6 enzyme.
This was assessed in vitro by determining the capacity of a compound of the invention to enhance sodium nitroprusside-induced relaxation of pre-contracted rabbit corpus cavernosum tissue strips, as described by S. A. Ballard et al. (Brit. J. Pharmacol., 1996, 118 (suppl.), abstract 153P).
Compounds were screened in anaesthetised dogs to determine their capacity, after i.v. administration, to enhance the pressure rises in the corpora cavernosa of the penis induced by intracavernosal injection of sodium nitroprusside, using a method based on that described by Trigo-Rocha et al. (Neurourol. and Urodyn., 1994, 13, 71).
Compounds of the invention may be tested at varying i.v and p.o. doses in animals such as mouse and dog, observing for any untoward effects.